Automatic apparatus for counting suspended particles in liquids

ABSTRACT

An automatic apparatus is disclosed for counting suspended particles in liquids. The apparatus comprises a first vessel having a sample of test fluid contained therein. A second vessel is adapted to be partially immersed into the first vessel. An aperture is formed in the second vessel to enable the sample fluid to be drawn from the first vessel into the second. The size of the aperture is dimensioned to enable one particle at a time to pass therethrough during the fluid flow. A piston pump is connected via a conduit to the second vessel to draw the sample fluid from the first vessel, through the aperture and into the first vessel during its suction stroke, and to reverse the flow of sample fluid during the pressure stroke. Electrodes are positioned within first and second vessels to establish a current in the fluid contained in the two vessels. During the fluid flow, impedance variations are formed as the particles pass through the aperture. These impedance variations are transformed into countable electrical impulses by suitable electrical equipment. To ensure that the second vessel is completely evacuated at the end of each test cycle, an auxiliary air chamber is positioned adjacent the piston cylinder to introduce an additional amount of air during the pressure stroke of the pump.

United States Patent [191 Thoma AUTOMATIC APPARATUS FOR COUNTING SUSPENDED PARTICLES IN LIQUIDS Josef Thoma, Waldkirch, Germany 22 Filed: Dec. 15, 1972 [21] Appl. No.: 315,408

[75] Inventor:

[30] Foreign Application Priority Data Mar. 26, 1974 5 7 ABSTRACT An automatic apparatus is disclosed for counting suspended particles in liquids. The apparatus comprises a first vessel having a sample of test fluid contained therein. A second vessel is adapted to be partially immersed into the first vessel. An aperture is formed in the second vessel to enable the sample fluid to be drawn from the'first vessel into the second. The size of the aperture is dimensioned to enable one particle at a time to pass therethrough during the fluid flow. A piston pump is connected via a conduit to the second Dec 31 1971 Germany 2165836 vessel to draw the sample fluid from the first vessel, through the aperture and into the first vessel during its [52] us Cl 324/71 CP suction stroke, and to reverse the flow of sample fluid [51] Int Cl n 27/00 during the pressure stroke. Electrodes are positioned [58] Field of "2 73/425 within first and second vessels to establish a current in 5 the fluid contained in the two vessels. During the fluid flow, impedance variations are formed as the particles 56] keferencescited pass through the aperture. These impedance variations are transformed into countable electrical impulses by v UNITED STATES PATENTS suitable electrical equipment. To ensure' that the sec- 3,654,55I Flinchbaugh Cp nd vessel is completely evacuated at the end of each 3'577'l62 Gaehwle' at 324/71 CP x test cycle, an auxiliary air chamber is positioned adja- 53:22: et 23 cent the piston cylinder to introduce an additional 3'O15775 H1962 Coulter CP amount of air during the pressure stroke of the pump,

Primary Examiner-Alfred E. Smith Assistant ExaminerRolf Hille 4 Claims, 1 Drawing Figure Attorney, Agent, or FirmRobert M. Vargo Mfl/dQ 5V0- Maw/5w 53 6/ r9 5 J I 5/ 3 5 Mp DUZWMM A/W/Q cam/r52 BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to devices for counting suspended particles in liquids and more particularly to devices for counting erythrocytes and/or leukocytes in blood.

2. Description of the Prior Art In the type of devices described above, the suspended particles in blood are usually counted by first diluting the blood with an electrical conducting, physiological fluid and pouring the diluted mixture into a vessel. The fluid is then pumped from the vessel, through a tiny aperture and into a second vessel. The size of the aperture is dimensioned to permit only one particle at a time to pass therethrough. Electrodes are then immersed in the fluid in both vessels to establish a current through the fluid located therein. The applied measuring method is based on the fact that, as the electrical current is passing through the sample fluid, impedance variations appear whenever the suspended particles pass through the aperture. These measurable impedance variations are then transformed into countable electrical impulses.

In the prior art devices, the sample fluid is usually pumped from the first vessel to the second and then back again. The first count of the fluid travel from the first to the second vessel is then compared with the count of the reverse travel. The pumping is usually accomplished with a piston pump connected to the second vessel via a conduit. In the pumping procedure, the suction stroke of the piston causes fluid to be drawn from the first vessel, through the aperture and into the second vessel. The pressure stroke of the piston then reverses the flow to force the fluid out of ,the second vessel, back through the aperture and into the first vessel. After all the fluid has been forced outof the second vessel, the first vessel with the fluid sample contained therein is then removed from the apparatus and another vessel filled with a fluid sample is connected to the second vessel for another test run.

The shortcoming with the prior art devices is that, quite often in the two-stage pumping process, the second stage pumping fails to force all of the fluid drawn into the second vesselback out to the first vessel. As a result, the residue that remains in the second vessel makes it necessary to discontinue the test runs until the second vessel is removed and cleaned. This procedure, of course, is very cumbersome and time-consuming.

SUMMARY OF THE INVENTION The present invention obviates the above-mentioned shortcoming by providing a particle-counting apparatus that is capable of totally evacuating the second vessel of any sample fluid during each pressure stroke. This total evacuation is accomplished by providing an auxiliaryair inlet communicating with the pump piston cylinder to draw in atmospheric air during the pistons lowermost travel and feed additional air into the pump chamber during the pistons uppermost travel. As a result, this additional motive fluid during the pressure stroke of the pump ensures the total evacuation of the second chamber.

The primary advantage of the present invention is that sequential test runs of different fluid samples can be continuously conducted without having to interrupt the procedure because the second vessel needs clean- BRIEF DESCRIPTION OF THE DRAWINGS The FIGURE is a schematic view of the counting apparatus of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, the FIGURE illustrates an automatic apparatus 10 for counting suspended particles in liquid. Although the liquid can be any type of liquid having particles in it, the present invention is particularly adapted to be utilized in counting erythrocytes and/or leukocytes in blood. In the preferred embodiment, the blood is first diluted with an electrical conducting, physiological fluid and is poured as a mixture 11 into a first vessel 13. The apparatus further comprises a second vessel 15 which is adapted to be positioned within the first vessel 13. The second vessel 15 includes an aperture 17 that is dimensioned to enable one particle at a time to pass through the aperture 17 as the fluid is flowing therethrough. For example, in the preferred embodiment, the diameter of the aperture 17 is um to accommodate the blood cells.

The top of the second vessel 15 is enclosed with a cork or plug 19 and is connected via a tube 21 to a cylindrical pump chamber 23 of a piston pump 25. The piston pump 25 comprises a cylindrical wall 27 closed at its lower end 29 and open to the atmosphere at its upper end 31. A piston 33 is slidably mounted within the cylindrical wall 27 with the lower face 35 thereof cooperating with the cylindrical wall 27 and the closed end 29 to form the pumping chamber 23. The piston 33 is connected via a rod 37 to a motor 39 to be reciprocally driven thereby. I

Electrical current is established in the fluid 11 passing from the first vessel 13 to the second vessel 15 by means of a pair of electrodes 41 and 43. The first electrode 41 extends nearly to the bottom of the second vessel 15, whereas the second electrode 43 extends within the first vessel 13 a distance slightly below the lower extension of the second vessel 15. A third electrode 45 extends into the second vessel 15 and terminates at a point higher within the second vessel 15 than the firstelectrode 41. The first and second electrodes 41 and 43 are connected via lines 47 and 49 to an amplifier 51 which, in turn, is serially coupled to a discriminator 53 and a counter 55. The first electrode 41 and the third electrode 45 are also connected via lines 57 and 59 to a servo-mechanism 61 which, in turn, is coupled to the pump motor 39. A switch 63 is also coupled to the pump motor 39.

An auxiliary air chamber 65 is adapted to communicate with the interior of the cylindrical wall 27. The mouth of the conduit 67 is positioned to be located below the lower face 35 of the piston 33 when the piston is in its uppermost position (shown in solid lines). This mouth location is also above the upper face of the piston 33 when the piston 33 is in its lowermost position (shown in broken lines) to communicate with the atmosphere.

OPERATION In operation, the fluid mix 11 is first deposited in the first vessel 13 and the vessel is positioned as shown in the FIGURE. At this time, the piston 33 is in its lowermost position. The swtich 63 is then turned on to actuate the pump motor 39 and start the piston 33 on its suction stroke. As the piston 33 is being raised, a suction is created within the pumping chamber 23, the tube 21 and the second vessel 15. This suction causes the liquid level within the second vessel 15 to rise. As the liquid level reaches and contacts the first electrode 41, an electrical circuit is closed between the first electrode 41 and the second electrode 43. As the liquid level continues to rise in the second vessel 15, due to the suction stroke of the piston 33, impedance variations appear whenever the suspended particles within the fluid pass through the aperture 17. These measurable impedance variations are transmitted through the lines 47 and 49 to the amplifier 51 and transformed into countable electrical impulses by the electrical components comprising the amplifier 51, the discriminator 53, and the counter 55.

As the liquid level reaches and contacts the second electrode 43, the signal generated thereby is fed to the servomechanism 61 which, in turn, functions to restart the counting components 51, 53, and 55 along with reversing the drive of the pump motor 39. This reverse drive causes the piston 33 to move downwardly in its pressure stroke. During the pressure stroke, the piston 33 functions to force the liquid out of the second vessel 15 back through the aperture 17 into the first vessel 13. During this phase, the counting is repeated until the liquid level extends below the first electrode 41. At this time the established current between the first and second electrodes 41 and 43 is broken. However, the pump 33 continues to move downwardly until it reaches the end of its stroke to completely force out all ofthe remaining fluid within the second vessel 15. Normally, even without the help of the auxiliary air chamber 65, the pumping action of the pressure stroke would be sufficient to force all of the liquid out of the second vessel 15. However, in practice, it has been found that the pumping action alone would leave a small quantity of liquid within the second vessel 15. Therefore, in accordance with the present invention, the auxiliary air chamber 65 is provided to add an additional volume of motive fluid during the pressure stroke to ensure that the entire amount of fluid is pumped out of the second vessel 15. As stated previously, the air chamber 65 communicates with the atmosphere when the piston 33 is in its lowermost position. During the suction stroke of the piston 33, the air chamber 65 is closed off from the atmosphere by the piston 33. As the lower face 35 of the piston 33 approaches the end of its suction stroke, it passes the opening of the conduit 67 to enable the air chamber 65 to communicate with the pumping chamber 23. Because the pumping chamber 23 is at a lower pressure than the air chamber 65, the air contained within the auxiliary air chamber 65 is drawn out into the pumping chamber 23. Thereafter, during the pressure stroke of the piston 33, the additional volume of air will combine with the motive fluid already contained within the pumping chamber to pump the entire amount of liquid of the second vessel 15. As a result, the second vessel 15 need not be cleaned for the next test run. All that is necessary is that a new vessel 13 with a new liquid sample be positioned as shown in the FIGURE. The entire process is then repeated as described above.

It should be noted that various modifications can be made to the apparatus while still remaining within the purview of the following claims. For example, the auxiliary air supply can be accomplished by an aperture formed on the cylinder wall 27 that communicates directly with the atmosphere. The location of the aperture would be at the same location as the mouth 67 of the air chamber 65.

What is claimed is:

1. An automatic apparatus for counting suspended particles in liquid comprising:

a first vessel having a sample of liquid contained therein;

a second vessel adapted to be in fluid communication with said first vessel via an aperture, said aperture being dimensioned to permit one particle at a time to pass therethrough;

means for passing a current through the liquid moving between the vessels via said aperture;

means for measuring the impedance variations of the liquid due to the passing of particles through said aperture;

means for pumping the liquid from said first vessel through said aperture to said second vessel during the first cycle and from said second vessel, through said aperture to said first vessel during the second cycle, said pumping means comprising a piston movably mounted within a cylindrical chamber forming the pumping chamber, said pumping chamber communicating with said second vessel via a conduit; and

means for adding auxiliary motive fluid to said pumping means during said second cycle to ensure that the entire amount of liquid drawn into said second vessel is pumped out of said second vessel at the end of said cycle, said auxiliary motive fluid means comprising an air chamber in communication with said pumping chamber at a point which is below the upper most travel of the piston.

2. The invention of claim 1 wherein said point where the air chamber communicates with said piston cylinder is above the lowermost travel of the piston to enable the air chamber to communicate with the atmosphere.

3. The invention of claim 1 wherein said means for passing a current through the liquid comprises a first and second electrode mounted within said first and second vessels respectively.

4. The invention of claim 3 further comprising a third electrode mounted with said second vessel at a position above said second electrode, said third electrode being connected to said measuring means for deactivating said measuring means when said liquid, having a current passing therethrough, contacts said third electrode. 

1. An automatic apparatus for counting suspended particles in liquid comprising: a first vessel having a sample of liquid contained therein; a second vessel adapted to be in fluid communication with said first vessel via an aperture, said aperture being dimensioned to permit one particle at a time to pass therethrough; means for passing a current through the liquid moving between the vessels via said aperture; means for measuring the impedance variations of the liquid due to the passing of particles through said aperture; means for pumping the liquid from said first vessel through said aperture to said second vessel during the first cycle and from said second vessel, through said aperture to said first vessel during the second cycle, said pumping means comprising a piston movably mounted within a cylindrical chamber forming the pumping chamber, said pumping chamber communicating with said second vessel via a conduit; and means for adding auxiliary motive fluid to said pumping means during said second cycle to ensure that the entire amount of liquid drawn into said second vessel is pumped out of said second vessel at the end of said cycle, said auxiliary motive fluid means comprising an air chamber in communication with said pumping chamber at a point which is below the upper most travel of the piston.
 2. The invention of claim 1 wherein said point where the air chamber communicates with said piston cylinder is above the lowermost travel of the piston to enable the air chamber to communicate with the atmosphere.
 3. The invention of claim 1 wherein said means for passing a current through the liquid comprises a first and second electrode mounted within said first and second vessels respectively.
 4. The invention of claim 3 further comprising a third electrode mounted with said second vessel at a position above said second electrode, said third electrode being connected to said measuring means for deactivating said measuring means when said liquid, having a current passing therethrough, contacts said third electrode. 